Catalpa tree with worms - Ask Extension
I had planted hundred of catalpa trees. They seem growing easily until last week I noticed one (about 20' tall) with almost no leaf left (Pics. 1 &am...
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Catalpa tree with worms #840272
Asked July 12, 2023, 12:11 PM EDT
I had planted hundred of catalpa trees. They seem growing easily until last week I noticed one (about 20' tall) with almost no leaf left (Pics. 1 & 2). Then this morning I notice a small one (about only 3' tall) with similar situation (Pic. 3). Also noticed was several worms on this smaller three. Any pesticide I can use to kill these worms to avoid they spreading out? So far other catalpa trees seem alright.
Oakland County Michigan
Expert Response
Good Morning,
Healthy catalpa trees can withstand complete defoliation by catalpa worms and will often push out a second set of leaves if defoliation happens early in the season. So one tactic is to ensure catalpa trees are healthy enough to withstand defoliation via proper water and fertilizer regimes and accept sporadic catalpa worm outbreaks as a consequence of growing catalpa trees. During large outbreaks, smaller individual branches may be killed, but this is unlikely to affect the long-term health of the tree.
Repeated outbreaks of catalpa worms over multiple seasons or multiple outbreaks in one season where multiple generations occur may damage and kill catalpa trees, especially trees that are already weakened by stress or disease. Some trees are defoliated more frequently and may be more attractive to catalpa sphinxes than others. The reasons for this are unclear but may be tied to the genetics of individual trees. If an individual tree is continuously defoliated by catalpa worms and appears to be in decline, it may be best to remove and replace it with a catalpa with different genetics or with a different tree species altogether.
If control is desired, there are a number of tactics that can be employed. First, egg masses, which are often obvious on the undersides of leaves, can be removed and destroyed. When catalpa trees are small, the caterpillars can be trimmed out (if they're young and gregarious) or handpicked and drown in a bucket of soapy water. Caterpillars that are parasitized should be left on the tree in order to allow the parasitoids to emerge. In the fall or early spring, after the caterpillars burrow into the soil to pupate and before the adult moths emerge, the soil around the tree can be tilled in an effort to destroy the pupae. When caterpillars first emerge and are small, products that contain Bt can be applied to the tree to kill them. Broad-spectrum insecticides should be avoided because of their detrimental impacts to natural enemies, which may make subsequent outbreaks worse.
Catalpa Worm/ Catalpa Sphinx Moth (psu.edu)
You may want to have an arborist come out and assess your trees. TreesAreGood.org
I hope this helps. Thanks for using our service.
Healthy catalpa trees can withstand complete defoliation by catalpa worms and will often push out a second set of leaves if defoliation happens early in the season. So one tactic is to ensure catalpa trees are healthy enough to withstand defoliation via proper water and fertilizer regimes and accept sporadic catalpa worm outbreaks as a consequence of growing catalpa trees. During large outbreaks, smaller individual branches may be killed, but this is unlikely to affect the long-term health of the tree.
Repeated outbreaks of catalpa worms over multiple seasons or multiple outbreaks in one season where multiple generations occur may damage and kill catalpa trees, especially trees that are already weakened by stress or disease. Some trees are defoliated more frequently and may be more attractive to catalpa sphinxes than others. The reasons for this are unclear but may be tied to the genetics of individual trees. If an individual tree is continuously defoliated by catalpa worms and appears to be in decline, it may be best to remove and replace it with a catalpa with different genetics or with a different tree species altogether.
If control is desired, there are a number of tactics that can be employed. First, egg masses, which are often obvious on the undersides of leaves, can be removed and destroyed. When catalpa trees are small, the caterpillars can be trimmed out (if they're young and gregarious) or handpicked and drown in a bucket of soapy water. Caterpillars that are parasitized should be left on the tree in order to allow the parasitoids to emerge. In the fall or early spring, after the caterpillars burrow into the soil to pupate and before the adult moths emerge, the soil around the tree can be tilled in an effort to destroy the pupae. When caterpillars first emerge and are small, products that contain Bt can be applied to the tree to kill them. Broad-spectrum insecticides should be avoided because of their detrimental impacts to natural enemies, which may make subsequent outbreaks worse.
Catalpa Worm/ Catalpa Sphinx Moth (psu.edu)
You may want to have an arborist come out and assess your trees. TreesAreGood.org
I hope this helps. Thanks for using our service.
